From: Finetti Noemi <noemi.finetti@aquila.infn.it>

Date: Fri Mar 28 2008 - 11:09:18 CET

Date: Fri Mar 28 2008 - 11:09:18 CET

Dear Alberto and Francesco,

I am trying to describe an uniform isotropic flux of cosmic protons on a

sphere of radius 7.1 cm. Since SFLOOD generates a random position and

direction on an unit radius sphere (1 cm, right?) it could be useful

(thanks for your advice!).

Moreover ... Francesco was right about the problem concerning the error

in linking Fluka with CERN Library: I forgot the option -C when I

launched the lflukac! Now it works! Thanks!

At present I am reading data from an external data file but I would like

to generate events directly with Fluka (work in progress). One more

question ... from Fluka on-line manual I read something about "Sampling

from a generic distribution" but it is not clear to me how I can find

with Fluka the inverse value XX=F-1(t) of the cumulative distribution of

a given function ("fu" in my source subroutine) by interpolation.

noemi

Alberto Fasso' wrote:

*>Dear Noemi,
*

*>
*

*>I discussed it with Francesco, and it is not clear to us which kind of
*

*>isotropic source you intend to implement, since you are reading your cosines
*

*>from an external file. The solution suggested by him (reproduced below) and
*

*>by Sebastien (using the RACO routine) apply only to an isotropic point source.
*

*>But if you are trying to describe a uniform isotropic flux inside a certain
*

*>volume (as I suspect since you are dealing with cosmic rays) the correct
*

*>routine to use is SFLOOD:
*

*>
*

*> SUBROUTINE SFLOOD ( XXX, YYY, ZZZ, UXXX, VYYY, WZZZ )
*

*>
*

*>* This is a subroutine of FLUKA9x/200x for sampling a random *
*

*>* position and direction on a unit radius sphere, such that to *
*

*>* generate a uniform and isotropic fluence inside *
*

*>
*

*>Note that SFLOOD generates a random position on a sphere of radius 1, so you
*

*>will have to normalize it to the actual radius of the sphere where you want
*

*>a uniform isotropic field.
*

*>
*

*>A discussion on SFLOOD can be found on the archive of this list, see
*

*>http://www.fluka.org/web_archive/earchive/new-fluka-discuss/0919.html
*

*>and the 4 following mails
*

*>
*

*>Alberto
*

*>
*

*>On Thu, 27 Mar 2008, Francesco Cerutti wrote:
*

*>
*

*>
*

*>
*

*>>But you can implement an isotropic sampling directly in your source routine,
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*>>according to the Sebastien's suggestion or, e.g., sampling uniformly between
*

*>>ZERZER and TWOPIP the azimuthal angle and between -ONEONE and ONEONE the
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*>>cosine of the polar angle.
*

*>>
*

*>>
*

*>
*

*>
*

*>
*

-- Address: Dott.ssa Noemi Finetti c/o Dipartimento di Fisica dell'Universita' di L'Aquila Via Vetoio - 67010 Coppito - L'Aquila - Italy Phone(office):+39-0862-433051; Fax(department):+39-0862-433033 "NON SI NASCONDE FUORI DEL MONDO CHI LO SALVA E NON LO SA. E' UNO COME NOI, NON DEI MIGLIORI." EUGENIO MONTALEReceived on Fri Mar 28 11:27:01 2008

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